nuclear industry standard process radiological...

Portable Survey Instruments NISP-RP-001

Revision: 1

Industry Approval Date: September 14, 2018 This is an industry document for standardizing radiation protection processes. Standard processes and requirements are established to eliminate site-specific radiation protection procedures. The Institute for Nuclear Power Operations (INPO) maintains current procedures on the INPO website. Approval authority is granted by the industry contingent on a structured review and approval process by representatives of utility radiation protection organizations.

NUCLEAR INDUSTRY STANDARD PROCESS

Radiological Protection

Level 3 – Information Use

Nuclear Industry Standard Process Portable Survey Instruments

Document #: NISP-RP-001

Revision: 1

Table of Contents

1.0 Purpose ........................................................................................................................... 1

2.0 Scope ............................................................................................................................... 1

3.0 Definitions ........................................................................................................................ 1

4.0 Responsibilities ................................................................................................................ 1

5.0 General Requirements ..................................................................................................... 1

6.0 Process Instructions ........................................................................................................ 2

6.1 Perform Pre-Use Instrument Inspections and Checks ............................................. 2

6.2 Operate an Ion Chamber Survey Instrument ............................................................ 3

6.3 Operate a GM Survey Instrument ............................................................................ 4

6.4 Operate a Count Rate Meter with a GM Frisker Probe ............................................ 4

6.5 Operate a Count Rate Meter with an Alpha, Beta, or Dual Scintillation Probe ......... 4

6.6 Operate a Neutron Rem-meter ................................................................................. 5

7.0 Records/Documentation .................................................................................................. 5

8.0 References ...................................................................................................................... 5

8.1 Commitments ........................................................................................................... 5

8.2 General .................................................................................................................... 5

9.0 Attachments ..................................................................................................................... 6

9.1 Attachment 1: General Radiation Detector Types and Uses ................................... 7

9.2 Attachment 2: Typical Portable Detection Systems in Use at Nuclear Power Stations ................................................................................................................... 9



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1.0 Purpose

1.1 This procedure provides basic instructions to operate common instruments used for radiation and contamination surveys. General descriptions, operating characteristics and limitations of these instruments are provided as attachments.

2.0 Scope

2.1 This procedure provides guidance for the selection and operation of portable instruments that measure gamma, beta, alpha and neutron radiation. If supplemental personnel are expected to operate instruments beyond the scope of this procedure, additional training may be required consistent with the site training and qualification program.

2.2 The forms referenced by this procedure are examples used to describe the pertinent information that should be recorded for future reference. Plant procedures may specify the use of equivalent forms or the use of electronic media for the same purposes.

2.3 This procedure will be used to train supplemental radiological protection technicians. Current revisions are maintained on the INPO website.

3.0 Definitions

3.1 Terms, acronyms, and definitions are provided in NISP-RP-013, Radiological Protection Glossary.

4.0 Responsibilities

4.1 Radiation Protection is responsible for the implementation of this procedure per Efficiency Bulletin 17-01 and the Nuclear Industry Standard Process Initiative.

5.0 General Requirements

5.1 Ensure that selected survey instruments are appropriate and calibrated to detect the types of radiation present in the work area.

5.1.1 Ensure that instruments used to measure radioactivity count rate have a scale that reads in units of counts per minute (cpm) or a multiple of this unit.

5.1.2 Ensure that instruments used to measure gamma dose rate have a scale that reads in units of mR/hr or mrem/hr or a multiple of these units.

5.1.3 Refer to Attachment 1, “General Radiation Detector Types and Uses” for general information on instrument types and use.

5.1.4 Refer to Attachment 2, “Typical Portable Radiation Detection Systems in Use at Nuclear Power Stations” to obtain specific information about standard portable detection systems.



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5.1.5 Read all tags and labels on an instrument to determine if the use of a scale is restricted.

5.2 When using an instrument model for the first time, review the applicable manufacturer technical or operational manual, or operating procedure to understand the data display, control adjustments, and limits.

5.3 Ensure the instrument is turned on prior to entering an area to survey. Zero the instrument, if applicable, and ensure operational and functional checks were performed prior to entering the radiation field.

5.4 Prevent contamination of an instrument by avoiding contact with contaminated surfaces or bagging the instrument prior to use in a contaminated area.

5.5 Prevent damage to thin window detectors by avoiding contact with small, sharp objects.

5.6 Apply appropriate correction factors as provided by site procedures.

5.7 When using an instrument with an internal detector, use case markings to align the detector with radiation sources.

5.8 When using an instrument with an analog meter, allow the meter to recover/stabilize from inertial effects on the needle.

5.9 If the instrument has a scale adjustment, set the instrument on a scale appropriate for the expected dose rates prior to exposing the instrument to the radiation field.

5.9.1 Adjust scales with the objective to obtain a stabilized reading between 10% and 90% of the scale.

5.9.2 Allow the meter to stabilize after switching scales due to the potential for electronic noise to cause a temporary meter deflection.

5.9.3 Prevent instrument damage by avoiding exposure to excessive heat, moisture, and radiation fields that are significantly above full- scale of the instrument.

6.0 Process Instructions

6.1 Perform Pre-Use Instrument Inspections and Checks.

6.1.1 Inspect instruments for physical damage prior to and during use.

6.1.2 Ensure all cables are connected securely; verify no spikes or erratic results are displayed when moving cables.

6.1.3 Ensure switches and knobs can be operated without restriction.



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6.1.4 If using a scintillation detector, turn the instrument on and check for punctures in the detector window by exposing the detector to a light source. An increase in the background count rate may be indicative of a punctured window.

6.1.5 If damage is suspected, tag the instrument out of service and contact appropriate site instrument coordinator or supervisor.

6.1.6 Ensure the instrument has a calibration sticker affixed and that the calibration due date is in the future.

6.1.7 If the instrument has a Battery Check mode, perform a battery check and ensure that the reading is within the specified range.

6.1.8 When inspecting an instrument with an analog or digital meter, allow the meter to recover/stabilize from the inertial effects on the needle.

6.1.9 Ensure a source check per the required frequency has been performed on the scales expected to be used.

6.1.10 When performing source checks, use the identified source as provided in site specific procedures.

6.1.11 If the site uses an instrument accountability system, sign instruments out and in as appropriate.

6.2 Operate an Ion Chamber Survey Instrument

6.2.1 Determine the gamma dose rate by holding the instrument in a steady position with the window closed and allowing the readout to stabilize.

6.2.2 Determine the beta dose rate by obtaining open window and closed window readings with the instrument in the same position. Apply the following calculation:

𝐵𝑒𝑡𝑎 𝐷𝑜𝑠𝑒 𝑅𝑎𝑡𝑒 = ((𝑂𝑊 − 𝐶𝑊) × 𝐶𝐹𝛽)

where:

OW= Open window

CW= Closed window

CFβ= Beta Correction Factor (provided on an instrument label or in station procedures)

6.2.3 Measure the activity on a highly contaminated smear (e.g. > 100,000 dpm) by placing the open window as close as possible to the smear without touching it and observe the digital display or meter indication.



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6.2.4 Apply correction factors as provided by site procedures as needed to convert readings to dpm/100 cm2 (e.g. 75,000 dpm/mR per hour of Cs-137).

6.3 Operate a GM Survey Instrument

6.3.1 Determine the gamma dose rate by holding the instrument in a steady position and allowing the display to stabilize.

a. If the detector has a beta window, ensure the window is closed during gamma measurement.

6.3.2 Exercise caution if a reading is off-scale high or low due to the potential for over-ranging conditions that may damage the instrument.

a. Remove the instrument from the radiation field and/or change scales to prevent over-ranging conditions.

6.4 Operate a Count Rate Meter with a GM Frisker Probe

6.4.1 Turn on the count rate meter and allow approximately 10 seconds for an analog count rate meter to stabilize.

6.4.2 Estimate background by setting the range switch on the lowest range with an on-scale reading and setting the response time to the slowest setting, if adjustable.

6.4.3 Determine the count rate by multiplying the value indicated on the meter by the scale factor shown on the range selector switch.

6.4.4 Frisk surfaces as instructed in NISP-RP-002, Radiation and Contamination Surveys.

6.4.5 Convert count rate readings (CPM) to disintegration rate (DPM) as follows:

a. For pancake GM detectors, multiply the CPM meter reading by 10 or as directed by RP supervision.

6.4.6 Press the reset button to clear alarms as needed.

6.5 Operate a Count Rate Meter with an Alpha, Beta, or Dual Scintillation Probe

6.5.1 Turn on the count rate meter and allow approximately 10 seconds for an analog count rate meter to stabilize

6.5.2 For instruments with multiple channels for alpha, beta, or dual response, ensure the instrument is set to appropriate mode corresponding to the probe being used.

6.5.3 Maintain the protective cover over the detector when not in use to prevent puncturing the thin film window.



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6.5.4 Estimate background radiation level by setting the range switch on the lowest range that provides an on-scale reading.

a. When using a dual scintillation probe for both alpha and beta readings, ensure that separate background readings are measured.

6.5.5 Determine the count rate by multiplying the value indicated on the meter by the scale factor shown on the range selector switch.

a. Some digital instruments may automatically switch ranges and directly show the corresponding cpm values.

6.5.6 Frisk surfaces as instructed in NISP-RP-002, Radiation and Contamination Surveys.

6.5.7 Convert count rate readings (CPM) to disintegration rate (DPM) as follows:

a. Multiplying the meter reading by the factor labeled on the instrument or as provided by RP supervision.

b. When using a dual alpha and beta scintillation probe, ensure that the appropriate factors are applied to alpha and beta readings.

6.6 Operate a Neutron Rem-meter

6.6.1 Turn on the analog neutron rem-meter and allow approximately 10 seconds for the meter to stabilize.

6.6.2 Determine the neutron dose rate by holding the instrument in a steady position allowing the readout to stabilize.

6.6.3 If required by site procedures, apply correction factors to meter results to get corrected readings.

7.0 Records/Documentation

NONE

8.0 References

8.1 Commitments

NONE

8.2 General

8.2.1 NISP-RP-002, Radiation and Contamination Surveys



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9.0 Attachments

9.1 Attachment 1: General Radiation Detector Types and Uses

9.2 Attachment 2: Typical Portable Detection Systems in Use at Nuclear Power Stations



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ATTACHMENT 1 General Radiation Detector Types and Uses

Page 1 of 2

General Types of Radiation Detectors

There are several types of radiation detectors used in the nuclear industry, some of the more common detector

types are listed below along with general information on detector type, their operation, and use. This list of

instruments is not all inclusive, other types of instruments may be used provided they are in accordance with

manufacturers recommendations or site specific procedures.

Gas-filled Detectors

All gas-filled detectors require a voltage be applied between a center anode and the detector chamber (cathode). As

a radiation particle or photon enters the chamber, it ionizes gas atoms creating positive ions and free electrons which

are captured by the positive charge on the anode and negative charge on the cathode. The collection of these ions

and electrons creates a pulse which is sensed and converted by the instrument’s electronic circuitry to provide an

accurate display of the measured contamination or radiation fields depending on the type of instrument. By varying

the voltage on the chamber, three useful types of gas-filled detectors can be created; Geiger-Mueller (GM)

detectors, proportional counters, and ionization chambers.

The gas inside the detectors can vary depending on design and use. Certain gas-filled detectors operate on normal

air while others use specialty gas.

GM detectors have a relatively high voltage (approximately 1000 - 1400 volts) applied to the chamber and as such,

every particle or photon entering the chamber creates enough secondary ionizations that the entire chamber is

ionized producing one large pulse.

Proportional counters have typically less voltage applied than GM detectors (approximately 300 –800 volts)

which can vary depending on its use. Because the voltage is typically less, proportional detectors can be set up to

produce pulses that are proportional to the energy of the incident radiation and therefore can be used to differentiate

between alpha and beta particles. Common hand-held proportional detectors include both gas-flow and sealed

chambers. Gas-flow proportional detectors require a constant flow of gas through the chamber in order to operate.

Ionization chambers require varying amount of voltage (approximately 50 - 300 volts) and are designed to produce

outputs which are relative to the incident energy of the photons or particles and thus can be calibrated to be relatively

energy independent.

Ionization chambers are one of the preferred detectors for measuring gamma dose rates because they can measure

deep dose equivalent and tend to be accurate over a wide range of gamma energies. Ionization chambers have

varying responses to neutron radiation due to recoil protons

Scintillation Detectors

Certain crystals, plastics, liquids and other materials will “scintillate”, or give off visible light, when they absorb

ionizing radiation. The amount of light emitted is proportional to the amount and energy of ionizing radiation that

they absorb. When coupled with a photomultiplier tube or photo cathode (devices which convert visible light into

electronic pulses) these materials make very useful radiation detectors. Scintillation detectors are widely used to

detect alpha, beta, and gamma radiation and can be used to measure gamma dose rate and contamination.

Because the properties of certain materials allow them to absorb radiation differently, certain scintillation detectors

are more useful than others for specific radiation types. There are many types of scintillation materials and

detectors, but the common ones used for hand-held applications in the nuclear power industry are:



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ATTACHMENT 1 General Radiation Detector Types and Uses

Page 2 of 2

Zinc Sulfide (ZnS) Detectors are generally used to measure alpha contamination. A thin layer of ZnS effectively

absorbs the energy from alpha particles and produces light but the ZnS layer does not have the characteristics to

efficiently absorb beta particles or photons. ZnS detectors are excellent detectors for detecting low levels of alpha

particles because of their inherently low response to background.

Plastic Scintillator Detectors are typically used to detect beta and gamma radiation. Thin layers of plastic

scintillators are very effective in measuring beta particles and very low energy photons, such as those emitted from

Iodine-125. Thin plastic scintillators are too thick to produce light from alpha particles and are not large enough to

absorb gamma rays of moderate energy and thus are very good beta detectors.

Thick plastic scintillators absorb moderate to higher energy photons effectively and can be used for measuring

gamma dose rate and gamma rays from contamination but are too thick to effectively absorb alpha or beta particles

and covert them to measurable light. Plastic scintillator detectors are very popular because plastic can be molded

in a variety of configurations to provide specialty application. Thick plastic scintillation detectors are often used in

vehicle monitors, tool monitors, and some hand-held instruments, such as micro-rem meters.

Sodium Iodide Detectors (NaI)

Sodium Iodide (NaI) crystals are used in a variety of applications and are very effective in detecting gamma photons.

Thick NaI detectors are very sensitive to gamma radiation and can be used for gamma monitoring and gamma

spectroscopy. Detectors with thin NaI crystals can be effectively used to measure lower energy photons and are

mostly used in medical applications.

Cesium Iodide Detectors (CsI)

Cesium Iodide (CsI) crystals are used in some portable detectors for measuring gamma radiation. Handheld systems

with CsI detectors are also used to perform gamma spectroscopy and can be used for underwater applications.

Dual Scintillation Detectors

Some detector probes contain a combination of scintillation material allowing them to detect more than one type of

radiation simultaneously. Common types of dual scintillation probes contain a thin plastic scintillator with a coating

of ZnS. These probes are effective in surveying for both alpha and beta particles at the same time and if used with

the appropriate electronics, can provide a separate readout for alpha and beta count rate.

Semi-Conductor Detectors

Semi-conductor detectors (sometimes referred to as “solid-state” detectors) have properties midway between a

good conductor and a good insulator and can act much like an ionization chamber. Common materials used to

make semi-conductor detectors includes Germanium and Silicon. Germanium detectors are often used for gamma

spectroscopy and laboratory applications; however, Silicon has been widely used to make portable detection

systems including alarming dosimeters, air monitors, and some area monitors.

Nuclear Industry Standard Process

Portable Survey Instruments


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ATTACHMENT 2 Typical Portable Detection Systems in Use at Nuclear Power Stations

Page 1 of 7

Manufacturer Model(s) Detector

Type

Typical Use Typical

Range

Notes and Special

Considerations

Image

Ludlum 12-4 Internal He3

Proportional

Counter

General area

neutron dose rate

surveys

4 Ranges

0 to 10,000

mRem/hr

• Instrument provides

gamma background

rejection up to 12

R/hr.

Ludlum 14-C Internal GM

Probe for

dose rate

monitoring

External

Pancake GM

Detector for

count rate

monitoring

Internal probe can

be used for dose

rate monitoring

External Pancake

probe used for beta

contamination

monitoring

Internal

Probe:

5 Ranges

0 to 2 R/hr

External

Probe:

4 Ranges

0 to 660K

cpm

• Ensure that the

selector switch is set to

the correct detector

(i.e. internal vs.

external) to ensure

proper result.

Ludlum 177 Beta +

Gamma

GM 0 cpm -

500k cpm • Meter face can have

both mR/hr and cpm

readouts. User must

be aware of the probe

and calibration and use

proper scale




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Page 2 of 7


Type

Typical Use Typical

Range • Notes and Special

Considerations

Image

Ludlum 3 External

Pancake GM

Detector for

count rate

monitoring

External Pancake

probe used for beta

contamination

monitoring

External

Probe:

4 Ranges

0 to 500K

cpm

• Meter face can have

both mR/hr and cpm

readouts. User must



proper scale

Ludlum 3 Gamma GM 0 - 200

mR/hr • Meter face can have

both mR/hr and cpm

readouts. User must



proper scale

Ludlum 9-7 Beta +

Gamma

Ion Chamber, 2

detectors

LOW:

0.001 –

1.99 R/hr

MID:0.1 -

199.9 R/hr

HIGH:0.01-

19.9 KR/hr

• Can be used with low,

mid, and high range

probes

• Digital readout

• Similar controls to

RO-7




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Page 3 of 7


Type

Typical Use Typical

Range

Notes and Special

Considerations

Image

Ludlum 3000 The Model

3000

utilizes an

external

radiation

detector to

detect alpha,

beta, or

gamma

radiation.

Geiger-Mueller

(GM), scintillator,

or proportional

0.0 cps to

99.9 kcps &

0.00 cpm to

999 kcpm

0.00 Bq to

99.9 kBq &

0.00 dpm to

999 kdpm

0.00µR/h to

999 R/h &

0.00µSv/h

to 999 Sv/h

• Auto Ranging

• Rate, Max, and Count

Modes of Operation

• All-Digital Calibration




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Page 4 of 7


Type

Typical Use Typical


Considerations

Image

Mirion AMP-

50/100/200

Internal

Energy

Compensated

GM Tube

Remote area

monitor or

underwater detector

AMP-50:

10uR/hr to 4

R/hr

AMP-100:

0.005 R/hr to

1,000

R/hr

AMP-200:

0.5 R/hr to

10,000 R/hr

• Cables can be up to

350’ long

• Unit can be used with

WRM wireless

transmitters

Mirion Ram Gam-

1

Internal

energy

compensated

GM tube

General area and

contact gamma dose

rate surveys. Often

used for shipping

surveys since it can

get close to packages

for contact readings.

0.05mR/hr

to

999mR/hr

• Digitial Instrument

Mirion RDS-30 Internal

energy

compensated

GM tube

General area and

contact gamma dose

rate surveys. Often

used for shipping

surveys since it can

get close to packages

for contact readings.

1 uRem/hr

to 10

Rem/hr

• Digital instrument

• Needs factory software

to calibrate




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Page 5 of 7


Type

Typical Use Typical


Considerations

Image

Mirion RDS-31 Internal

energy

compensated

GM tube

General area and

contact gamma

dose rate surveys.

Often used for

shipping surveys

since it can get

close to packages

for contact

readings.

1 uRem/hr

to 10

Rem/hr

• Digital instrument

• Needs factory software

to calibrate

Mirion Telepole 2 Internal

energy

compensated

GM tubes

1 high range,

1 low range

General-area and

contact gamma

dose rate surveys.

Can be used for

shipping surveys

since it can get

close to packages

for contact readings

0.05 mR/hr

to 1000

R/hr

Pole extends 11’

Thermo

Eberline

6112B

Teletector

2 internal

GM

Detectors for

Low and

High Range

General-area and

contact gamma

dose rate surveys

5 Ranges

0.1 mR/hr

to 1000R/hr

• Detectors extend to

approximately 13’




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Page 6 of 7


Type

Typical Use Typical


Considerations

Image

Thermo

Eberline

E-140 External GM

probe

General area and

contact gamma

dose rate surveys.

Often used for

shipping surveys

since it can get

close to packages

for contact

readings.

0 to 200

mR/hr

when

calibrated

to dose rate

• Meter face has both

mR/hr and cpm

readouts. User must



proper scale.

Thermo

Eberline

(formally

Bicron)

Microrem Gamma + X-

Ray

TEP Scintillator 5 Ranges

0 - 200

mRem/hr

• Tissue equivalent and

flatter energy response

than Ludlum Micro-R

Thermo

Eberline

RM-14 External

Pancake GM

Detector for

count rate

monitoring

External Pancake

probe used for beta

contamination

monitoring

External

Probe:

3 Ranges

0 to 50K

cpm

• Can be used with both

a GM pancake probe

or with an end-

window GM probe in

a fixed counting

holder




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Page 7 of 7


Type

Typical Use Typical


Considerations

Image

Thermo

Eberline

RO 2/2A Internal Ion

Chamber

General-area

gamma and beta

dose rate surveys

RO-2:

4 Ranges

0.1 mR/hr

to 5 R/hr

RO-2A

4 Ranges

1 mR/hr to

50 R/hr

• Has two battery

checks for each of the

two batteries

• Significant changes in

atmospheric pressure

or temperature can

affect reading and

require re-calibration

Thermo

Eberline

RO 20 Internal Ion

Chamber

General-area

gamma and beta

dose rate surveys

5 Ranges

0.1 mR/hr

to 50 R/hr

• Updated model of the

RO-2 which includes

the additional RO-2A

range

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